A seizure may be characterized as abnormal or excessive synchronous activity in the brain. At the beginning of a seizure, neurons in the brain may begin to fire at a particular location. As the seizure progresses, this firing of neurons may spread across the brain, and in some cases, many areas of the brain may become engulfed in this activity. Seizure activity in the brain may cause the brain to send electrical signals through the peripheral nervous system to different muscles the activation of which may manifest as an electrical signal at the surface of the skin near a muscle.
Techniques designed for studying and monitoring seizures have typically relied upon electroencephalography (EEG), which characterizes electrical signals using electrodes attached to the scalp or head region of a seizure prone individual or seizure patient. Detecting an epileptic seizure using electroencephalography (EEG) typically requires attaching many electrodes and associated wires to the head and using amplifiers to monitor brainwave activity. The multiple EEG electrodes may be very cumbersome and generally require some technical expertise to apply and monitor. Confirmation of a seizure typically requires observation in an environment provided with video monitors and video recording equipment. Furthermore, when measuring brain activity with EEG, not all measured activity of or relating to a seizure may actually be manifested as an event that is likely to be dangerous. And, EEG data without video corroboration may not be suited to grade or differentiate some seizures, including those that may be weak or only of minimal concern, from other seizures that may be more dangerous.
Unless used in a staffed clinical environment, EEG equipment is frequently not intended to determine if a seizure is in progress but rather provide a historical record of the seizure after the incident. EEG equipment is usually designed for hospital-like environments where a video camera recording or caregiver's observation may provide corroboration of the seizure, and is typically used as part of a more intensive care regimen such as a hospital stay for patients who experience multiple seizures. A hospital stay may be required for diagnostic purposes or to stabilize a patient until suitable medication can be administered. Upon discharge from the hospital, a patient may be sent home with little further monitoring.
A patient should in some cases be monitored at home for some length of time in case another seizure should occur. Seizures with motor manifestations may have patterns of muscle activity that include rhythmic contractions of some, most, or all of the muscles of the body. A number of health concerns may develop from this activity. A seizure could, for example, result in Sudden Unexplained Death in Epilepsy (SUDEP). The underlying causes of SUDEP are not well understood; however, in some cases, severe central nervous system (CNS) depression may follow a seizure. Following central nervous system depression, breathing rates may increase and decrease in a cycle that may result in cardiac dysrhythmia and death. However, not all seizures have the same likelihood of causing or being associated with SUDEP, and in some patients, some seizure activity may be present without significant risk of SUDEP. And, without differentiation of seizures by type, severity or further classification, it may be difficult to selectively identify seizure activity that is most likely to be dangerous.
While there presently exist ambulatory devices for diagnosis of seizures, they are EEG-based and are generally not designed or suitable for long-term home use or daily wearability. Other seizure alerting systems may operate by detecting motion of the body, usually the extremities. Such systems may generally operate on the assumption that while suffering a seizure, a person will move erratically and violently. However, depending upon the type of seizure, this assumption may or may not be true. Electrical signals sent from the brain during the seizure are frequently transmitted to many muscles simultaneously, which may result in muscles fighting each other and effectively canceling out violent movement. In other words, the muscles may work to make the person rigid rather than cause actual violent movement. Thus, seizure activity may not be consistently detected with accelerometer-based detectors.
Accordingly, there is a need for seizure detection methods and apparatuses that can be used in non-institutional or institutional environments without many of the cumbersome electrodes to the head or extremities and that accurately detect seizure events with motor manifestations. There is also a need for epileptic seizure detection methods that differentiate weak motor manifestation that may not demand an emergency response from other types of seizures including those that may demand emergency intervention.